First measurements of triton burnup neutron spectra using a natural diamond detector on JT-60U

A natural diamond detector (NDD) is one of the candidates for the DT neutron spectrometer in the International Thermonuclear Experimental Reactor since it has a high energy resolution, a high radiation resistance and a very compact size. The characteristic performance of NDD as a DT neutron spectrometer was examined at the FNS neutron generator. The NDD indicated the energy resolution of 1.95% to 14.1 MeV neutrons. In order to obtain the information of the triton slowing-down, the NDD was applied to the deuterium discharges of the JT-60U tokamak. By accumulating the data of several shots, the change of the pulse height spectrum suggesting the slowing-down of tritons was observed after neutral beam turn-off.